1. Technical Field
The disclosure relates to aperture and projection devices and, particularly, to a dynamic aperture and a projection device having the same.
2. Description of the Related Art
In digital light processing (DLP) projectors, digital micro-mirror devices (DMDs) as spatial light modulators, which bit-depth is limited, cannot reproduce low-level signals typical of most video sources. Therefore, a gain is applied to the input signal to obtain more dynamic range for the projection. However, since the input signal has been electrically amplified, it is necessary to optically reduce the brightness of the corresponding image to appropriate levels by use of an aperture in the light path of the DLP projectors. Furthermore, the aperture and gain must be dynamically determined frame-by-frame.
FIG. 4 shows an alternative proposed aperture 2. The aperture 2 includes a motor 3, a disc 4, and a stop rod 7. The disc 4 is installed to the motor 3 providing rotation of the disc 4 and defines two slots 5 shaped in an Archimedean spiral. One of the slots 5 is positioned in the light path to adjust light throughput. The other slot 5 is coupled to the stop rod 7 which can be controlled to stop the rotating disc 4 at an appropriate position to produce a desired light throughput. A shortcoming of the aperture 2 is that a narrow, thick connection portion 6 between the slots 5 can be easily broken by the stop rod 7, shortening service time of the aperture 2.
Therefore, it is desirable to provide a dynamic aperture and a projection device having the same, which can overcome the described limitations.